Biodegradable materials for bone defect repair.

Compared with non-degradable materials, biodegradable biomaterials play an increasingly important role in the repairing of severe bone defects, and have attracted extensive attention from researchers. In the treatment of bone defects, scaffolds made of biodegradable materials can provide a crawling bridge for new bone tissue in the gap and a platform for cells and growth factors to play a physiological role, which will eventually be degraded and absorbed in the body and be replaced by the new bone tissue. Traditional biodegradable materials include polymers, ceramics and metals, which have been used in bone defect repairing for many years. Although these materials have more or fewer shortcomings, they are still the cornerstone of our development of a new generation of degradable materials. With the rapid development of modern science and technology, in the twenty-first century, more and more kinds of new biodegradable materials emerge in endlessly, such as new intelligent micro-nano materials and cell-based products. At the same time, there are many new fabrication technologies of improving biodegradable materials, such as modular fabrication, 3D and 4D printing, interface reinforcement and nanotechnology. This review will introduce various kinds of biodegradable materials commonly used in bone defect repairing, especially the newly emerging materials and their fabrication technology in recent years, and look forward to the future research direction, hoping to provide researchers in the field with some inspiration and reference.

Testing bioresorbable stent feasibility in a rat aneurysm model.

BACKGROUND: Advances in stent-assisted coiling have incrementally expanded endovascular treatment options for complex cerebral aneurysms. After successful coil consolidation and aneurysm occlusion, endovascular scaffolds are no longer needed. Thus, bioresorbable stents that disappear after aneurysm healing could avoid future risks of in-stent thrombosis and the need for lifelong antiplatelet therapy. OBJECTIVE: To assess the applicability and compatibility of a bioresorbable magnesium- alloy stent (brMAS) for assisted coiling. METHODS: Saccular sidewall aneurysms were created in 84 male Wistar rats and treated with brMAS alone, brMAS + aspirin, or brMAS + coils + aspirin. Control groups included no treatment (natural course), solely aspirin treatment, or conventional cobalt-chromium stent + coils + aspirin treatment. After 1 and 4 weeks, aneurysm specimens were harvested and macroscopically, histologically, and molecularly examined for healing, parent artery perfusion status, and inflammatory reactions. Stent degradation was monitored for up to 6 months with micro-computed and optical coherence tomography. RESULTS: Aneurysms treated with brMAS showed advanced healing, neointima formation, and subsequent stent degradation. Additional administration of aspirin sustained aneurysm healing while reducing stent-induced intraluminal and periadventitial inflammatory responses. No negative interaction was detected between platinum coils and brMAS. Progressive brMAS degradation was confirmed. CONCLUSIONS: brMAS induced appropriate healing in this sidewall aneurysm model. The concept of using bioresorbable materials to promote complete aneurysm healing and subsequent stent degradation seems promising. These results should encourage further device refinements and clinical evaluation of this treatment strategy for cerebrovascular aneurysms.

Expert Consensus on Absorbable Advanced Suspension Technology for Facial Tissue Repositioning and Volume Enhancement.

BACKGROUND: Signs of facial aging include wrinkles, loss of subcutaneous volume, decreased tone, texture, and sagging of the skin. The objective of this review is to determine whether facial suspension absorbable sutures are a safe and effective modality for facial rejuvenation.

METHOD: A group of US plastic surgeons and dermatologists who practice medical aesthetics convened to review evidence obtained from literature searches and to reach a consensus on clinical practice guidelines for the use of facial absorbable suspension sutures.

RESULTS: Currently, there are different types of lifting sutures available. Absorbable, facial suspension sutures allow for superior repositioning of tissue along a vector line together with the added benefit of volumization of the area. These benefits are for patients who have moderate facial aging and require treatment beyond the use of injectable products only.

CONCLUSIONS: Treatment with absorbable facial suspension sutures, when performed properly, is associated with minor and infrequent complications and offers a beneficial clinical alternative to traditional facial rejuvenation techniques.

J Drugs Dermatol. 2017;16(7):661-666.

Regulatory Considerations in the Design and Manufacturing of Implantable 3D-Printed Medical Devices.

Three-dimensional (3D) printing, or additive manufacturing, technology has rapidly penetrated the medical device industry over the past several years, and innovative groups have harnessed it to create devices with unique composition, structure, and customizability. These distinctive capabilities afforded by 3D printing have introduced new regulatory challenges. The customizability of 3D-printed devices introduces new complexities when drafting a design control model for FDA consideration of market approval. The customizability and unique build processes of 3D-printed medical devices pose unique challenges in meeting regulatory standards related to the manufacturing quality assurance. Consistent material powder properties and optimal printing parameters such as build orientation and laser power must be addressed and communicated to the FDA to ensure a quality build. Postprinting considerations unique to 3D-printed devices, such as cleaning, finishing and sterilization are also discussed. In this manuscript we illustrate how such regulatory hurdles can be navigated by discussing our experience with our group's 3D-printed bioresorbable implantable device.

Biodegradable cisplatin-eluting tracheal stent for malignant airway obstruction: in vivo and in vitro studies.

BACKGROUND: Self-expandable metallic stents (SEMSs) are effective in the palliation of malignant airway obstruction. Tumor ingrowth, however, frequently occurs because of a shortage of effective local therapy. Additionally, SEMSs are frequently associated with problems of fracture, migration, and difficult removals. Our goal was to develop a novel bioabsorbable stent with cisplatin elution to circumvent such problems. METHODS: Biodegradable stents made of polycaprolactone were fabricated by a laboratory-made, microinjection molding machine. In vitro mechanical strength of the stents was compared with the strength of Ultraflex SEMSs. Polylactide-polyglycolide copolymer and cisplatin were coated onto the surfaces of the stents. Elution method and high-performance liquid chromatography (HPLC) analysis were used to examine the in vitro cisplatin release characteristics. In vivo, the stents were surgically implanted into the cervical trachea of 15 New Zealand white rabbits. Bronchoscopic examination was performed weekly (1 to approximately 5 weeks) before killing. Cisplatin concentrations in trachea, lung, and blood were analyzed by HPLC. Histologic examination was also performed. RESULTS: The biodegradable stent exhibited mechanical strength comparable to the strength of Ultraflex SEMSs and provided a steady release of cisplatin for >4 weeks in vitro. The in vivo study showed sustained cisplatin levels in rabbit trachea for >5 weeks with a minimum drug level in blood. Histologic examination showed an intact ciliated epithelium and marked leukocyte infiltration in the submucosa of the stented area. CONCLUSIONS: Our study demonstrated that the biodegradable stents provided physical properties comparable to the properties of SEMSs and a sustained release of cisplatin for >5 weeks, which showed great potential in the treatment of malignant airway obstruction.

Osteolysis following resorbable poly-L-lactide-co-D, L-lactide PLIF cage use: a review of cases.

STUDY DESIGN: Report of case series. OBJECTIVE: To report a problem with bioabsorbable poly-L-lactide-co-D, L-lactide, PLDLLA, posterior lumbar instrumented fusion (PLIF) cage implants. SUMMARY OF BACKGROUND DATA: Synthetic bioabsorbable implants have recently been introduced to spinal surgery and their indications and applications are still being explored. There is evidence that the use of bioabsorbable cages may be of benefit in interbody spinal fusion. METHODS: We present a case series of nine patients who have undergone PLIF with bioabsorbable cages in the lumbar spine. RESULTS: At follow-up over at least 1 year, four of these patients were found to have osteolysis around the implant on CT scanning. One of these patients underwent an operation to remove the cage and histology sent during surgery suggested that the implant had caused the bone loss and there was no evidence of infection. Another patient had ongoing pain in relation to the lysis, while the other two patients with lysis remained asymptomatic. CONCLUSIONS: PLDLLA cage, which has high osteolytic nature, is considered not suitable as a fusion cage.

Radiation and ethylene oxide terminal sterilization experiences with drug eluting stent products.

Radiation and ethylene oxide terminal sterilization are the two most frequently used processes in the medical device industry to render product within the final sterile barrier package free from viable microorganisms. They are efficacious, safe, and efficient approaches to the manufacture of sterile product. Terminal sterilization is routinely applied to a wide variety of commodity healthcare products (drapes, gowns, etc.) and implantable medical devices (bare metal stents, heart valves, vessel closure devices, etc.) along with products used during implantation procedures (catheters, guidewires, etc.). Terminal sterilization is also routinely used for processing combination products where devices, drugs, and/or biologics are combined on a single product. High patient safety, robust standards, routine process controls, and low-cost manufacturing are appealing aspects of terminal sterilization. As the field of combination products continues to expand and evolve, opportunity exists to expand the application of terminal sterilization to new combination products. Material compatibility challenges must be overcome to realize these opportunities. This article introduces the reader to terminal sterilization concepts, technologies, and the related standards that span different industries (pharmaceutical, medical device, biopharmaceuticals, etc.) and provides guidance on the application of these technologies. Guidance and examples of the application of terminal sterilization are discussed using experiences with drug eluting stents and bioresorbable vascular restoration devices. The examples provide insight into selecting the sterilization method, developing the process around it, and finally qualifying/validating the product in preparation for regulatory approval and commercialization. Future activities, including new sterilization technologies, are briefly discussed.

Evaluation of bioabsorbable multiamino acid copolymer/α-tri-calcium phosphate interbody fusion cages in a goat model.

STUDY DESIGN: A study of cervical interbody fusion using polyamino acid-based bioabsorbable fusion cages in a goat model. OBJECTIVE: To compare interbody fusion of a bioabsorbable multiamino acid copolymer/α-tri-calcium phosphate (MAACP/α-TCP) fusion cage with an autologous tricortical iliac-crest bone graft and a titanium cage. SUMMARY OF BACKGROUND DATA: Polyamino acid is widely used as a carrier for drug delivery. To our knowledge, no study investigates interbody fusion cage made of polyamino acid. METHODS: A total of 15 sheep underwent C3/C4 discectomy and fusion. The following stabilization techniques were used: group A, autologous tricortical iliac crest bone graft (n = 5); group B, MAACP/α-TCP cage filled with autologous cancellous bone graft (n = 5); group C, titanium cage filled with autologous cancellous bone graft (n = 5). Radiographic scans to determine disc space height were performed before and after surgery and after 4, 8, and 12 weeks, respectively. After 12 weeks, the C3/C4 motion segment was isolated and sectioned to create a 5-mm thick parasagittal section from which lateral radiographs were obtained. All the radiographs were encoded and reviewed in a blinded fashion to evaluate interbody fusion within the cage devices according to a three-point radiographic score. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending to determine range of motion (ROM). Histomorphological and histomorphometrical analyses were performed to evaluate fusion and foreign-body reactions associated with the bioabsorbable cages. RESULTS: Radiographic results showed that the disc space height (DSH) in MAACP/α-TCP cage group was better than that of bone graft group and the best radiographic score was found in MAACP/α-TCP cage group. Biomechanical test showed that no significant difference was found in ROM between MAACP/α-TCP cage group and titanium cage group whereas the value of ROM in bone graft group was the largest. Histologic evaluation showed a higher intervertebral bone volume/total volume ratio and a better interbody fusion in the MAACP/α-TCP cage group than in the other two groups. Two MAACP/α-TCP cages showed microcracks and the other three cages had maintained their original geometry. All MAACP/α-TCP cages showed excellent biocompatibility. CONCLUSION: After 12 weeks, there was no significant difference between the MAACP/α-TCP cage and the titanium cage in distractive properties and biomechanical properties. Compared with titanium cages, MAACP/α-TCP cages showed an advanced interbody fusion. Although MAACP/α-TCP cages developed cracks after only 12 weeks, they showed significantly better distractive properties, biomechanical properties, and an advanced interbody fusion than the tricortical iliac crest bone graft. Improvement should be made to insure the strength of MAACP/α-TCP cage last at least 6 month after implantion.

Biodegradation of porous calcium phosphate scaffolds in an ectopic bone formation model studied by X-ray computed microtomograph.

Three types of ceramic scaffolds with different composition and structure [namely synthetic 100% hydroxyapatite (HA; Engipore), synthetic calcium phosphate multiphase biomaterial containing 67% silicon stabilized tricalcium phosphate (Si-TCP; Skelite) and natural bone mineral derived scaffolds (Bio-oss)] were seeded with mesenchymal stem cells (MSC) and ectopically implanted for 8 and 16 weeks in immunodeficient mice. X-ray synchrotron radiation microtomography was used to derive 3D structural information on the same scaffolds both before and after implantation. Meaningful images and morphometric parameters such as scaffold and bone volume fraction, mean thickness and thickness distribution of the different phases as a function of the implantation time, were obtained. The used imaging algorithms allowed a direct comparison and registration of the 3D structure before and after implantation of the same sub-volume of a given scaffold. In this way it was possible to directly monitor the tissue engineered bone growth and the complete or partial degradation of the scaffold. Further, the detailed kinetics studies on Skelite scaffolds implanted for different length of times from 3 days to 24 weeks, revealed in the X-ray absorption histograms two separate peaks associated to HA and TCP. It was therefore possible to observe that the progressive degradation of the Skelite scaffolds was mainly due to the resorption of TCP. The different saturation times in the tissue engineered bone growth and in the TCP resorption confirmed that the bone growth was not limited the scaffold regions that were resorbed but continued in the inward direction with respect to the pore surface.

Tensile strength and adhesion formation of mesh fixation systems used in laparoscopic incisional hernia repair.

BACKGROUND: Mesh tearoff from the tissue is the most common reason for hernia recurrence after hernia surgery involving the use of a synthetic mesh. Various fixation systems were critically compared in terms of their retention strength and the formation of adhesions. METHODS: In a prospective study with 25 Sprague-Dawley rats, two pieces of Parietex composite meshes measuring 2 x 3 cm were fixed intraperitoneally in a paramedian location. The randomized mesh fixation groups included transfascial fixed suture, ProTack, AbsorbaTack, and I-Clip. Of the 25 rats, 12 were killed and analyzed 1 week after implantation, with the remaining 13 rats killed and analyzed after 2 months. Adhesions observed at the time of mesh removal were measured according to an adhesion scoring system, and the fixation strengths of the individual fixation systems were tested. Additionally, the foreign body reaction to the mesh and fixation systems was measured as well as their potential degradation. RESULTS: After 1 week, the retention strength of transfascial fixed suture was significantly higher (8.7 N/cm(2)) than that of ProTack (5.6 N/cm(2)) or AbsorbaTack (5.7 N/cm(2)). After 2 months, the retention strength had increased to 13.2 N/cm(2) in the transfascial fixed suture group, which was significantly higher than in the ProTack (9.7 N/cm(2)) or AbsorbaTack (8.7 N/cm(2)) groups. In contrast, the mesh could be fixed with the I-Clip only in 56% of the cases, and then achieved rather poor retention strength. Adhesion was significantly greater in the ProTack group than in any of the other groups (p < 0.001). At 2 months, scanning electron microscopy showed only marginal degradation of the absorbable elements. CONCLUSIONS: Suture fixation led to satisfactory attachment of the prosthesis. Additional widespread anchorage of the mesh was achieved with ProTack or AbsorbaTack. The feasibility and retention strength of the I-Clip were poor.

Use of bioabsorbable plates for cranial fixation.

LactoSorb fixation plates are made of a bioabsorbable polymer (82% poly-L-lactic acid and 18% polyglycolic acid), and the strength is not inferior to titanium plates. LactoSorb has been used in the fields of pediatric neurosurgery and facial plastic surgery. Cranial fixation in craniotomy is mostly performed using titanium plates and clamps, but there are issues with esthetics and artifacts on postoperative radiographic images. Absorbable plates solve these problems, but are slightly thicker and more expensive. Here, we describe a technique to solve these disadvantages by inserting absorbable plates into the diploe. The present method was employed in 46 patients, and esthetically favorable results were obtained without intraoperative and postoperative complications. Absorbable plates may replace titanium plates as the main device for cranial fixation. The present method is particularly useful for cranial fixation in adults with a thin scalp.

Engineering angiogenesis following spinal cord injury: a coculture of neural progenitor and endothelial cells in a degradable polymer implant leads to an increase in vessel density and formation of the blood-spinal cord barrier.

Angiogenesis precedes recovery following spinal cord injury and its extent correlates with neural regeneration, suggesting that angiogenesis may play a role in repair. An important precondition for studying the role of angiogenesis is the ability to induce it in a controlled manner. Previously, we showed that a coculture of endothelial cells (ECs) and neural progenitor cells (NPCs) promoted the formation of stable tubes in vitro and stable, functional vascular networks in vivo in a subcutaneous model. We sought to test whether a similar coculture would lead to the formation of stable functional vessels in the spinal cord following injury. We created microvascular networks in a biodegradable two-component implant system and tested the ability of the coculture or controls (lesion control, implant alone, implant + ECs or implant + NPCs) to promote angiogenesis in a rat hemisection model of spinal cord injury. The coculture implant led to a fourfold increase in functional vessels compared with the lesion control, implant alone or implant + NPCs groups and a twofold increase in functional vessels over the implant + ECs group. Furthermore, half of the vessels in the coculture implant exhibited positive staining for the endothelial barrier antigen, a marker for the formation of the blood-spinal cord barrier. No other groups have shown positive staining for the blood-spinal cord barrier in the injury epicenter. This work provides a novel method to induce angiogenesis following spinal cord injury and a foundation for studying its role in repair.

Practical limitations of bioresorbable membranes in the prevention of intra-abdominal adhesions.

INTRODUCTION: Intra-abdominal adhesions are a significant source of postoperative morbidity. Bioresorbable barriers composed of hyaluronic acid and carboxymethylcellulose (HA/CMC) reduce adhesion formation by physically separating injured or healing peritoneal surfaces. To assess whether the efficacy of a physical barrier can extend beyond the site of application, we evaluated the effectiveness of an HA/CMC barrier in preventing adhesions distal to the site of placement. METHODS: Adhesions were induced in rats by creating peritoneal ischemic buttons on either side of a midline incision. An HA/CMC barrier (Seprafilm Genzyme) was intraoperatively placed either under the midline incision, unilaterally over half the ischemic buttons, or bilaterally over all ischemic buttons. Control buttons received no HA/CMC. On day 7 adhesions were scored. In similar experiments, peritoneal fluid was collected at 24 h to assess the effects of HA/CMC on tissue plasminogen activator activity. RESULTS: Placement of HA/CMC under the midline incision did not reduce adhesion formation to distal ischemic buttons (72 +/- 7%) compared to controls (80 +/- 8%). Unilateral placement of HA/CMC significantly (p < 0.05) reduced adhesion formation to those ischemic buttons over which the barrier was applied (35 +/- 7%) compared to both contralateral (83 +/- 9%) and control (80 +/- 8%) ischemic buttons. The bilateral application of HA/CMC also significantly (p < 0.05) reduced adhesion formation to all ischemic buttons compared to controls (22 +/- 7% vs. 66 +/- 7%, respectively). HA/CMC did not affect peritoneal tPA activity. CONCLUSIONS: Effective adhesion reduction by the physical barrier HA/CMC appears to be limited to the site of application in this rat model. Despite the presence of a bioresorbable membrane at predicted sites of adhesion formation in the peritoneal cavity, adhesions readily form to distal unprotected sites.

Preliminary radiographic findings and sizing implications on patients undergoing bioabsorbable subtalar arthroereisis.

Metallic subtalar arthroereisis implants can require removal. Similarly configured bioabsorbable "interference screws" placed alternatively to metal implants may obviate removal. Radiographic imaging may show the location and sizing of the implant, and evaluate for implant degradation. Patients undergoing subtalar arthroereisis were evaluated with magnetic resonance imaging (computed tomography in one patient) to measure the size of the tarsal canal. The tarsal canal length, along with medial height and lateral height, were assessed. The patient's actual implant size was also noted as well as any signs of implant degradation, bony deformation, granulomas, and so forth. Six patients met the inclusion criteria. The range of implants used was 9 to 12 mm. The radiographic measurements of the tarsal canal were as follows: medial to lateral length, 12.8 +/- 3.4 mm; medial height, 7.3 +/- 2.5 mm; and lateral height, 8.0 +/- 1.7 mm. Two patients underwent implant removal. No cystic or degenerative changes were noted on plain radiographs with bioabsorbable implants. Bioabsorbable interference screws for subtalar arthroereisis placed in the tarsal canal may still require removal, although no detrimental changes were noted radiographically to the surrounding bony structures. The size of the current metallic implants on the market appears larger than the tarsal canal configuration.

Early failure of bioabsorbable anterior cervical fusion plates: case report and failure analysis.

STUDY DESIGN: Case report with forensic failure analysis. OBJECTIVE: To determine the failure modes of 3 explanted 70:30 PLDLA Mystique (Medtronic Sofamor Danek, Memphis, TN) graft containment plates retrieved from revision surgery for early device failure. SUMMARY OF BACKGROUND DATA: To reduce the problems of stress-shielding and radiopacity associated with metallic systems, bioabsorbable polymers have been used in anterior cervical discectomy and fusion procedures. Degradation of mechanical properties in vivo is a major concern when using bioabsorbable systems. Three of 6 patients who underwent anterior cervical discectomy with instrumented fusion, using Mystique graft containment systems experienced early failure requiring revision to alternate hardware. METHODS: Devices were retrieved after failure and analyzed by light microscopy and environmental scanning electron microscopy. Simulations were performed with an unused plating system to induce damage for comparison with the retrieved devices. A detailed case review was performed to identify possible sources of extraordinary loading or damage. RESULTS: One plating system failed at 6 weeks postimplantation due to fatigue fracture of the screws. Crack initiation sites were identified at the interface of the thread root and mold line of the screw. Another plating system failed at 16 weeks postimplantation due to the coalescence of radial microcracking between holes in the plate, leading to catastrophic failure of the plate. The final plating system failed during the implantation surgery, when the screw fractured in torsion. CONCLUSIONS: Stress concentrations at the screw head-shaft interface and thread-shaft interface reduce the fatigue performance of bioabsorbable screws. Hydrolysis of the polymer may also play a role in the reduction of resistance to crack initiation and propagation.

Bioabsorbable implants.

Absorbable implants have become the hottest implant material, overtaking titanium as the future. Absorbable devices have moved beyond orthopedics and maxillofacial surgery to spine, vascular, plastics and general surgery. This chapter outlines the experiences of many specialties.

Hybrid fixation improves structural properties of a free tendon anterior cruciate ligament reconstruction.

PURPOSE: This study sought to characterize the structural properties of a combined bioabsorbable interference screw and closed loop and button fixation technique (Hybrid) for femoral fixation of a free tendon graft versus a bioabsorbable interference screw or closed loop and button suspension fixation method alone. METHODS: Eighteen porcine femora and quadrupled cadaveric flexor tendons were treated in 3 experimental fixation study groups: (1) closed loop and button suspension (CLBS), (2) bioabsorbable interference screw (BIF), and (3) closed loop and button suspension with supplemental biodegradable interference screw (Hybrid). An Instron testing machine (Instron, Canton, MA) was used to quantify each group's structural properties with cyclic loading and tensile load-to-failure. A video digitizing system measured graft deformation during load-to-failure. RESULTS: The Hybrid fixation group had significantly greater structural properties compared with the CLBS or BIF group. Ultimate loads (mean [SEM] in Newtons) were 1184 (88) N, 813 (83) N, and 561 (62) N for the Hybrid fixation group, CLBS group, and BIF group, respectively. Quasi-steady state cyclic stiffness (mean [SEM] in Newtons per millimeter) was also greatest for the Hybrid fixation group at 165 (11) N/mm, compared with CLBS (122 [8] N/mm), and BIF (95 [9] N/mm). CONCLUSIONS: Femoral free tendon hybrid fixation provides superior structural properties under tensile and cyclic displacement conditions while preserving the working length of the native anterior cruciate ligament. CLINICAL RELEVANCE: Hybrid femoral fixation may minimize postoperative laxity for free tendon anterior cruciate ligament reconstruction.

Osteochondral graft fixation using a bioresorbable bone cement.

Multiple osteochondral grafts can be used to resurface large joint defects in both humans and horses. In humans, immediate postoperative weight bearing can be prevented, however in the equine, it is unavoidable. Early weight bearing can create detrimental graft micromotion. The aim of this study was to investigate the role of a bioresorbable cement in improving the initial stability of multiple osteochondral graft repairs of large subchondral cystic lesions in the horse. Configurations employed for filling a 20mm diameter cylindrical defect included: (A) twelve 4.5mm diameter grafts with cement, (B) five 6.5mm diameter grafts with cement, (C) four each of 4.5mm and 6.5mm grafts with cement and (D) cement only. Intact bone slices (E) were also tested. Push-out tests were used to quantify construct to host sidewall interface fixation. Configuration (A) proved clinically impractical (n=3). Configurations (B) (n=6), and (C) (n=4) had statistically similar interface stiffnesses and failure stresses (43+/-8 and 30+/-12 MPa and 0.96+/-0.1 and 1.2+/-0.3 Mpa, respectively) suggesting that they are equally susceptible to interface movement in the immediate postoperative period. By way of comparison, defects filled only with cement had an average stiffness of 53+/-7MPa and failure stress of 1.8+/-0.3 MPa (n=6) while the intact femoral condyle demonstrated a stiffness of 108+/-7 MPa and failure stress of 18+/-0.4 MPa (n=6). Cement augmentation improved immediate postoperative stability of multiple osteochondral graft constructs over uncemented constructs, although in all cases the observed moduli of elasticity and yield stress values were lower than those observed for cement only and intact bone test specimens. (all numbers are mean+/-SEM).

Ex vivo strength comparison of bioabsorbable tendon plates and bioabsorbable suture in a 3-loop pulley pattern for repair of transected flexor tendons from horse cadavers.

OBJECTIVE: To test the failure strength and energy of 2 bioabsorbable implants applied to transected deep digital flexor tendons (DDFT) from adult horses. STUDY DESIGN: Ex vivo biomechanical experiment. SAMPLE POPULATION: Twelve pairs of deep digital flexor tendons harvested from the forelimbs of fresh equine cadavers. METHODS: Poly-L-lactic acid tendon plates were custom manufactured for application to the cylindrical surface of an adult equine deep digital flexor tendon. Twelve pairs of DDFTs were transected 2 cm distal to the insertion of the distal check ligament of the deep digital flexor tendon. One tendon of each pair was randomly selected for repair with a biodegradable plate or a 3-loop pulley method. Size 2 polydioxanone suture was used in both repairs. Repairs were tested in tension to failure, with peak force (PF) and total energy (TE) at repair failure recorded in Newtons (N) and Joules (J), respectively. A paired t-test was used for statistical evaluation with a significant level set at P< or = .05. RESULTS: Mean+/-SD PF for failure of plated tendons (1507.08+/-184.34 N) was significantly greater than for sutured tendons (460.86+/-60.93 N). TE was also significantly greater for failure of plated tendons versus sutured tendons. CONCLUSIONS: Plate fixation of transected cadaver DDFTs appear to have superior immediate failure strength than 3-loop pulley repairs. CLINICAL RELEVANCE: Whereas in vivo testing is required, a bioabsorbable tendon plate may provide initial increased strength to support tendon healing and decrease external coaptation requirements.